Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin
Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin...
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ftmdpi:oai:mdpi.com:/2075-163X/13/1/62/ 2023-08-20T04:06:25+02:00 Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin Evgeniya N. Svetova Sergei A. Svetov agris 2022-12-30 application/pdf https://doi.org/10.3390/min13010062 EN eng Multidisciplinary Digital Publishing Institute Crystallography and Physical Chemistry of Minerals & Nanominerals https://dx.doi.org/10.3390/min13010062 https://creativecommons.org/licenses/by/4.0/ Minerals; Volume 13; Issue 1; Pages: 62 agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS C-O isotope genesis Text 2022 ftmdpi https://doi.org/10.3390/min13010062 2023-08-01T08:03:10Z Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, X-ray fluorescence spectrometry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and C-O isotope analysis were used for the study. Agate mineralization appears mostly as an infill of fissures, cavities, gas vesicles in massive and vesicular basalts, lava-breccias. The mineral composition of agates is dominated by alpha-quartz (fibrous chalcedony, microcrystalline and macrocrystalline quartz), but it also displays abundances of calcite. The characteristic red-brownish agate’s coloration is caused by multiple hematite inclusions distributed in an agate matrix. The study revealed the two phases of agate formation in the PrF volcanics, which are most likely controlled by two distinctly different fluids and/or their mixture. At first, agates appeared due to post-magmatic iron-rich fluids. The late hydrothermal activity was probably triggered by intrusion of gabbro-dolerite sill and resulted in the second phase of agate formation. We suggest that the late hydrothermal fluids remobilized the iron compounds from the crust of weathering underlying the PrF volcanics, which led to additional formation of vein agates and filling of gas vesicles with hematite-rich calcite/silica matter. Text Fennoscandia Fennoscandian MDPI Open Access Publishing Minerals 13 1 62 |
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Open Polar |
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MDPI Open Access Publishing |
op_collection_id |
ftmdpi |
language |
English |
topic |
agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS C-O isotope genesis |
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agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS C-O isotope genesis Evgeniya N. Svetova Sergei A. Svetov Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
topic_facet |
agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS C-O isotope genesis |
description |
Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, X-ray fluorescence spectrometry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and C-O isotope analysis were used for the study. Agate mineralization appears mostly as an infill of fissures, cavities, gas vesicles in massive and vesicular basalts, lava-breccias. The mineral composition of agates is dominated by alpha-quartz (fibrous chalcedony, microcrystalline and macrocrystalline quartz), but it also displays abundances of calcite. The characteristic red-brownish agate’s coloration is caused by multiple hematite inclusions distributed in an agate matrix. The study revealed the two phases of agate formation in the PrF volcanics, which are most likely controlled by two distinctly different fluids and/or their mixture. At first, agates appeared due to post-magmatic iron-rich fluids. The late hydrothermal activity was probably triggered by intrusion of gabbro-dolerite sill and resulted in the second phase of agate formation. We suggest that the late hydrothermal fluids remobilized the iron compounds from the crust of weathering underlying the PrF volcanics, which led to additional formation of vein agates and filling of gas vesicles with hematite-rich calcite/silica matter. |
format |
Text |
author |
Evgeniya N. Svetova Sergei A. Svetov |
author_facet |
Evgeniya N. Svetova Sergei A. Svetov |
author_sort |
Evgeniya N. Svetova |
title |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_short |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_full |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_fullStr |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_full_unstemmed |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_sort |
agates from mesoproterozoic volcanics (pasha–ladoga basin, nw russia): characteristics and proposed origin |
publisher |
Multidisciplinary Digital Publishing Institute |
publishDate |
2022 |
url |
https://doi.org/10.3390/min13010062 |
op_coverage |
agris |
genre |
Fennoscandia Fennoscandian |
genre_facet |
Fennoscandia Fennoscandian |
op_source |
Minerals; Volume 13; Issue 1; Pages: 62 |
op_relation |
Crystallography and Physical Chemistry of Minerals & Nanominerals https://dx.doi.org/10.3390/min13010062 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3390/min13010062 |
container_title |
Minerals |
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13 |
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1 |
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62 |
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1774717466120814592 |